Synthesis, Spectral Analysis, DFT Calculations, in Vitro Screening, and Molecular Docking of New Metal Complexes with Quinoline and Isoniazid Schiff Base as Antimicrobial and Antioxidant Agents

We herein report the synthesis, spectral analysis, DFT calculations, in vitro and in silico biological activities of novel N'-((2-thioxo-1,2-dihydroquinolin-3 yl)methylene)isonicotinohydr-azide with its Cu(II), Co(II), Ni(II), and Zn(II) complexes have been successfully prepared. The ligand and the complexes were characterized by analytical, FT-IR, ¹H NMR, mass, UV–visible spectroscopy, molar conductivity, and magnetic susceptibility measurements. Density Functional Theory (DFT) estimations for the ligand at the DFT/B3LYP level via 6-31 G⁺⁺ (d, p) replicate the structure and geometry. Furthermore, molecular docking and ADME calculations were also performed to correlate and interpret the experimental results. The antimicrobial activity study illustrated enhancement in the activity of the free ligand upon complex formation, and the Cu(II) complex (MIC 25 µg mL⁻¹) may be considered a promising antibacterial agent, and Ni(II) and Zn(II) complexes (MIC 25 µg mL⁻¹) as promising antifungal agent. Also, synthesized Ni(II) and Zn(II) metal complexes (MIC 3.125 µg mL⁻¹) showed promising anti-TB activity against Mycobacterium tuberculosis. In the antioxidant activity, the Cu(II) complex showed excellent activity as compared to standard drugs and in silico docking studies were carried out against Cytochrome c Peroxidase (PDB ID: 2X08).